NEW YORK — A certain shadow crosses the faces of hair-metal enthusiasts when they talk about 1991. Nirvana’s album “Nevermind” came out, and as swiftly as the Berlin Wall fell, the hair-metal musical genre nosedived from the top of the charts to the bargain bin.

Fans of hair metal — hard rock by guys who liked their hair big and their power ballads even bigger — were forced to retire their Poison and Skid Row T-shirts or face the scathing mockery of newly flannel-clad fans of Nirvana and other grunge groups.

“For years I loved the stuff,” said Nick Tyler, a 35-year-old computer programmer from Sydney, Australia. “The huge sound, the amazing guitar.”

“Everyone seemed to change their mind,” Tyler said. “The same people who owned all the same Mötley Crüe albums suddenly got into darker stuff and pretended they never liked metal in the first place.”

Tyler decided, as a matter of social survival, to keep his enthusiasm for the adrenaline-fueled, hairspray-frosted scene to himself.

But for many, love for hair metal was not destroyed — just tucked away along with 1989 tour memorabilia. Now, the Internet is allowing these fans to find their inner teenager, dust off their fandom and relive the days when rock stars dressed like rock stars, and music was delivered irony-free, one power-chord at a time.

Tyler can once again express his passion publicly without shame. He does so as a member of the Hair Metal Revival group on the social networking site Facebook, where he can virtually “throw up metal horns,” chat about bands, find links to videos and keep track of concert dates for the now-ubiquitous reunion tours.

Want to know where Kip Winger, former lead singer of the eponymous band, is playing soon? Most people do not, and it won’t be advertised on television, but the person who goes by “sydrock” helpfully posted dates, clips and a thoughtful review written from the perspective of a fan.

Hair metal, a strange fusion of the harder sounds of groups like Judas Priest and the addictive riffs of the fluffiest of pop, first made the national scene in the early 1980s.

Record labels soon caught on, and began promoting their own variations on the winning formula: dreamy singer + tight pants + pyrotechnics + power ballads + booze + makeup (sometimes) + hair gone wild. Early innovators Bon Jovi and Def Leppard were joined by groups like Cinderella and Winger.

By the late 1980s, the genre dominated MTV, which had become the new arbiter of popular music. Tuxedo-clad prom-goers pumped their fists to Bon Jovi’s “Livin’ on a Prayer” and frat boys took the lyrics of Mötley Crüe’s “Girls Girls Girls” to heart.

Record labels scanned the landscape for bands with ever more mass appeal, finally reaching the apogee (some would say abomination) with Nelson: the angelic-looking twin sons of crooner Ricky Nelson prancing around on stage in leather pants and headbands singing bouncy love songs.

“When people realized hair metal was a commodity that would sell, they brought in hair-metal producers, started marketing it, and it got kind of sanitized,” said Steve Peake, author of the “Guide to ’80s Music” on About.com.

Peake, 35, who grew up in North Carolina, remembers the days when it was OK to sport a mullet and your favorite band’s T-shirt. He confessed to having a hair-metal song — or two — in his iPod.

“There are certain things in my iPod that make me feel like I have to keep the volume down and the windows closed — hair metal is one of those things,” Peake said. “It just feels like something you’re supposed to be ashamed of.”

Still, he said, hair metal is not so different from other forms of guilty pleasure and does not necessarily deserve such harsh historical judgment.

“For almost everybody there is a recognition what they love or are enjoying is not the highest form of art,” he said.

The Web may, to some degree, be helping to correct the historical wrong, Peake added, as many bands have used it as a way to spark interest in revival tours.

Bon Jovi had the third-highest grossing tour of 2006, according to Billboard Boxscore, bringing in $131 million. Mötley Crüe’s last tour grossed a respectable $46.3 million.

“There’s no doubt that without the Internet we would not be holding reunions and revivals of all these bands,” Peake said. “There wouldn’t be a way to build a spark and turn it into a flame.”

These Internet communities are also a refuge for new fans, who cannot even use nostalgia as an excuse.

Chris Scaife, 24, discovered a certain predilection for the combination of melody, cheesy production and screeching guitars during high school in Stow, Ohio, he said, years after the music had gone out of style.

He heard Bon Jovi on the radio in his uncle’s car, bought their album “Slippery When Wet,” and “that was kind of it for me,” he said.

“The main thing is just the energy of it, very upbeat and loud,” Scaife said.

His friends at high school did not share his taste in music, he said, and were not sure what to make of the concert T-shirts and bandannas, “but they tried to understand.”

Still, he wanted more, so he went online.

Now, the senior psychology major at the University of Akron has found kindred spirits who are also members of several Facebook sites. Bolstered by the support, he has made his way to concerts by Poison, Def Leppard and other glam rock royalty.

“I don’t know any people otherwise who are fans like I am,” he said.

Other fans, still a bit downhearted about the position to which their favorite music has been relegated, take solace in the words of Mötley Crüe, which pop up frequently on groupie sites:

“One day you’ll walk into the tattoo shop of life and say: I’m back. I’m ready for my new tattoo, and her name is rock ‘n’ roll. You will have been through all the temporary 15 minutes of flash. You know what the man behind the counter will say? We knew you’d come back.”